At a photo session before the start of a meeting with Australian Prime Minister Robert Hawke yesterday, President Reagan was asked if he felt stabbed in the back by former Office of Management and Budget director David A. Stockman, whose still-unpublished memoir of the first Reagan administration is the talk of the town. Replied the president: "I won't comment. I don't have too much time for fiction."

Newsweek this week published excerpts of the Stockman book that portrayed Reagan as an amiable know-nothing whose closest aides were "illiterate when it came to the essential equation of policy," prompting one former colleague to describe the forthcoming book as a "kick and tell" memoir. Mail Bonding . . .

Alarums have been ringing for months over the rapid approach of the day when Congress will run out of money to pay for its mail. And the situation became grave on Tuesday when the House killed a $42.2 million supplemental appropriation to carry legislators through the remainder of the 1986 fiscal year.

So yesterday, the Senate acted -- sort of. The Senate Rules Committee approved a resolution "urging" House and Senate members to stay within their current budget of $95.7 million, and declaring a seven-day moratorium on the mass mailings to constituents that are legislators' life blood in an election year.

Once they have restrained themselves for a week, a tally will be taken of what remains in this year's $95.7 million mailing budget, and the remainder will be split 50-50 between the House and the Senate.